The purpose of this paper is to examine the ways how to determine the value of information in the information system. The information system in this paper is divided into two subsystems; information processing system and decision-making system, and each warrants different valuation-method. Under the former, information value should be determined from the information-producers point of view and its value measured by the amount of revenue generated. On the other hand, under the latter, it needs to be evaluated from the decision-maker`s or information user`s point of view and its worth measured by the expected payoff derived. The value-determination method in information system, so called an integrated system, could be applied to the measure of value under each subsystem, and this nesessitates introduction of a new concept, the net value of information. According to this concept, the net value of information is the amount derived from the information value less the information cost incurred. This net value is the criterion to determine the information value in the information subsystem or integrated system.